Cutting solutions are generally classified into water-soluble oil agents and water-insoluble oil agents, and they have the following characteristics, respectively.
First, a water-soluble oil agent has advantages whereby the processing precision can be increased since the cooling capability is excellent, and heating deterioration of tools can be prevented. Also, since the oil agent is used as a solution, it has an advantage whereby there is no danger of fire due to its non-flammability. However, since the agent is used as a solution diluted 10 to 50 times, in comparison with the water-insoluble oil agent, film strength is poor, and lubrication performance is also poor.
On the other hand, the water-insoluble oil agent has greater excellent effects as a cutting oil than the water-soluble oil agent whereby an excellent machined surface can be easily obtained due to excellent lubrication performance, and tools are not greatly worn. However, the water-insoluble oil agent is poorer in cooling capability and fire preventive performance than the water-soluble oil agent.
At a machining site, in accordance with an increase in rigidity of the machine, improvement in performance of tools, and improvement in machine controlling performance, the feeding speed can be increased, and the cutting area can be made larger. Therefore, the oil temperature easily rises as the cutting temperature rises, and in addition, the temperature at the cutting point also rises, whereby an ignition source area exceeding 500.degree. C. increases. And, the stronger an impact added, the higher the possibility of sparking, and therefore, the danger of fire increases.
Also, when the processing machine is auto-operated, sometimes broken tools remain at the machined portion, and if the next processing is applied to this machined surface, tools are forcibly pressed against this surface, and may cause excessive heating resulting in a fire.
Therefore, generally, regarding disaster prevention as important, a water-soluble oil agent is mostly used, however, regarding roughness of the machined surface and machining stability as important, sometimes a water-insoluble oil agent is used, and in this case, a situation where the machine is damaged by fire and must be discarded, or personal injury (burns) is caused occurs.
In view of the current circumstances where machining works show a tendency toward labor saving and automation, it is extremely preferable that machining stability can be pursued without worrying about disaster prevention if possible. Herein, it can be considered that an emulsifier is added to the water-insoluble cutting oil to be in a water containing condition, however, the contained moisture immediately disappears and flammability revives in actuality. For example, when the oil is used for a lathe, a water content of 10% in the morning changes to less than 1% by evening. Also, when an emulsifier is added to the water-insoluble cutting oil, the lubrication performance as a water-insoluble cutting oil is lost due to an influence from the emulsifier.
The invention is made in view of the above problems, and the themes thereof are to enable stable machining by using a water-insoluble oil agent, and provide a machining method with sufficient measures taken against disaster, and a cutting oil to be used in machining.